This invention is directed to lubricant compositions containing small additive concentrations of copper salts of thiodipropionic acid derivatives, the copper salts themselves and to their use as multifunctional antioxidant additives in lubricants and similar oleaginous fluids.
The use of sulfur compounds such as thioesters, dithiocarbamates, dithiophosphates, sulfurized olefins, sulfurized oils, and sulfurized fatty acid esters, have been well known for their antioxidant properties, as well as their antiwear, EP characteristics in a variety of products.
The use of copper carboxylates such as copper oleate has been reportedly used as an antioxidant by Exxon Corporation in British Patent No. 2,056,482 and in European Patent No. 92946 as an engine oil antioxidant.
The use of thiodipropionic esters such as dilauryl thiodipropioateniate are well known for their antioxidant properties in a variety of products including rubbers, plastics and lubricants.
It has now been found that the use of thiodipropionic acid derived copper salts in accordance with the invention provide exceptional multifunctional antioxidant activity, with potential anticorrosion, antiwear, and EP properties. The antioxidant activity demonstrated is greater than that reported for corresponding copper carboxylates or sulfur-containing compounds.